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Isn’t it weird, that each wine bottle smells so different although it is made from the same fruits? Indeed, grape varieties play an important role in the wine’s aroma profile¹. But there is another small player with a big impact. It’s yeasts. Yeasts are the organisms that transform sugars into alcohol and other molecules. During this process, called fermentation, these different molecules will influence and define the flavour, quality, and almost every aspect of your favourite wine².

In the wine field, yeasts are generally divided into two categories: Saccharomyces and non-Saccharomyces yeasts. This latter category encompasses many different species; among them, we could cite some of the most common ones, present in the vineyard on the grapes and that you may have heard of before, are Hanseniaspora spp., Candida spp., Metschnikowia pulcherrima or Lanchancea thermotolerans³. They all produce their unique cocktail of molecules that give unique flavors to the wine. It is still not fully understood how these microorganisms interactwith each other and what their oenological potential may be⁴.

However, in this article, we will concentrate on the chemical compounds released by these yeasts and the characteristics certain volatile molecules have on wine during fermentation. Those volatile compounds are majorly different from each yeast³.

For example, aromatic compounds like ethyl lactate and lactic acid, formed by L. thermotolerans. respectively add a creamy aspect to the mouthfeel and reduce the acidity and stinginess to create a softer body. M. pulcherrima. contributes to fruity notes such as pineapple and is also associated with other fruit aromas. For pear and apple aromas, their profile is similar to that of S. cerevisaie⁴.

On the other hand, not all chemical compounds contribute positively to wine aroma. Some microorganisms such as Brettanomyces bruxellensis produce some powerful aroma molecules that are associated with a cheesy smell, as well as with stable sometimes⁴.

But then who are we to judge if this is bad ? You may find those aromas a bit particular but quite fine !

In fact, some compounds are seen as a positive contribution if they appear in a small quantity as ethyl guaiacol and ethylphenol formed by B.bruxellensis., which adds a spicy, clove-like aroma for ethyl guaiacol and a little barnyard, leathery for ethylphenol. However, at high levels, the same compounds are considered a defect⁴. As the saying goes, “The dose makes the poison.”⁵. It is the same when considering Candida milleri. While acetic acid, produced as a byproduct of yeast metabolism, can contribute a pleasant freshness at low levels, excessive amounts can lead to vinegar-like aromas, which may negatively impact the wine’s quality⁴. Diacetyl is also an example of something desirable in a low amount but undesirable in a high amount. It gives buttery aromas which can also be unequilibrated in some wines⁴. Getting back to our main yeast, S.cerevisiae, produces byproducts like isoamyl acetate or isoamylol which adds a certain complexity at low concentrations but can be overwhelming at high concentrations⁴.

The balance between desirable and undesirable aromas depends on yeast species, fermentation conditions, winemaking practices, and your taste. What we do, is explore the biodiversity of yeasts and understand their metabolic pathways, which opens possibilities for tailoring wine aromas to enhance complexity and uniqueness. So, if this sparked your interest just continue visiting this site for regular updates on our work.